Pioneer Venus Multiprobe
Pioneer Venus Multiprobe
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| Mission type | Venus atmospheric probes |
|---|---|
| Operator | NASA / ARC |
| COSPAR ID | 1978-078A |
| SATCAT № | 11001 |
| Website | National Space Science Data Center (NASA) |
| Mission duration | 4 months, 1 day |
| Spacecraft properties | |
| Bus | HS-507 |
| Manufacturer | Hughes |
| Launch mass | 904 kilograms (1,993 lb) |
| Dry mass | 290 kilograms (640 lb) (bus) 315 kilograms (694 lb) (large probe) 3 x 90 kilograms (200 lb) (small probes) |
| Power | 241 watts |
| Start of mission | |
| Launch date | August 8, 1978, 07:33 UTC |
| Rocket | Atlas SLV-3D Centaur-D1AR |
| Launch site | Cape Canaveral LC-36A |
| End of mission | |
| Last contact | December 9, 1978, 20:22:55 UTC (bus) December 9, 1978, 20:55:34 UTC (day probe) |
| Orbital parameters | |
| Reference system | Heliocentric |
| Venus atmospheric probe | |
| Spacecraft component | Large Probe |
| Atmospheric entry | December 9, 1978, 18:45:32 UTC |
| Impact date | 19:39:53 UTC |
| Impact site | 4°24′N 304°00′E / 4.4°N 304.0°E |
| Venus atmospheric probe | |
| Spacecraft component | North Probe |
| Atmospheric entry | December 9, 1978, 18:49:40 UTC |
| Impact date | 19:42:40 UTC |
| Impact site | 59°18′N 4°48′E / 59.3°N 4.8°E |
| Venus atmospheric probe | |
| Spacecraft component | Day Probe |
| Atmospheric entry | December 9, 1978, 18:52:18 UTC |
| Impact date | 19:47:59 UTC |
| Impact site | 31°18′S 317°00′E / 31.3°S 317.0°E |
| Venus atmospheric probe | |
| Spacecraft component | Night Probe |
| Atmospheric entry | December 9, 1978, 18:56:13 UTC |
| Impact date | 19:52:05 UTC |
| Impact site | 28°42′S 56°42′E / 28.7°S 56.7°E |
| Venus atmospheric probe | |
| Atmospheric entry | December 9, 1978, 20:21:52 UTC |
The Pioneer Venus Multiprobe, also known as Pioneer Venus 2 or Pioneer 13 was a spacecraft launched in 1978 to explore Venus as part of NASA's Pioneer program.
The Pioneer Venus Multiprobe bus was constructed by the Hughes Aircraft Company, built around the HS-507 bus. It was cylindrical in shape, with a diameter of 2.5 metres (8 ft 2 in) and a mass of 290 kilograms (640 lb). Unlike the probes, which did not begin making direct measurements until they had decelerated lower in the atmosphere, the bus returned data on Venus' upper atmosphere.
The bus was targeted to enter the Venusian atmosphere at a shallow entry angle and transmit data until destruction by the heat of atmospheric friction. The objective was to study the structure and composition of the atmosphere down to the surface, the nature and composition of the clouds, the radiation field and energy exchange in the lower atmosphere, and local information on the atmospheric circulation pattern. With no heat shield or parachute, the bus made upper atmospheric measurements with two instruments, an Ion Mass Spectrometer (BIMS) and a Neutral Mass Spectrometer (BNMS), down to an altitude of about 110 km before disintegrating on December 9, 1978.
The spacecraft carried one large and three small atmospheric probes, designed to collect data as they descended into the atmosphere of Venus. The probes did not carry photographic instruments, and were not designed to survive landing - the smaller probes were not equipped with parachutes, and the larger probe's parachute was expected to detach as it neared the ground. All four probes continued transmitting data until impact; however, one survived and continued to transmit data from the surface.
The Large probe carried seven experiments, contained within a sealed spherical pressure vessel. The science experiments were:
This pressure vessel was encased in a nose cone and aft protective cover. After deceleration from initial atmospheric entry at about 11.5 kilometres per second (7.1 mi/s) near the equator on the night side of Venus, a parachute was deployed at 67 km altitude. The large probe was about 150 centimetres (59 in) in diameter and the pressure vessel itself was 73.2 centimeters (28.8 in) in diameter.
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